From CH 668 000 A5 a ski of even width is known, where a front section of the approximately flat sliding surface is bordered at the sides by two bevelled sections. The width of each of the bevelled sections normally increases steadily until they meet at the central axis of the ski at the transition between the main body and the tip. The bordered front section of the two bevelled side sections of the flat sliding surface is thereby normally approximately triangular in shape. Not only does the bevelling increase in width, but the angle of bevelling also increases towards the tip. The object is to reduce resistance during turning.
It is also normal for skis to be slightly wider at the front and the rear, i.e. the sides of the skis are gently curved. This helps to steer the skis through the turns with the least possible loss of kinetic energy. If the sides are curved too much, however, the skis will be difficult to control, since when they are on their edges they will cut into the snow at the front and the rear. Moreover, the grip on the snow in the middle of the ski will be reduced, which is a major disadvantage particularly on a hard cover, where everything depends on being able to skid well in the middle of the ski. For these reasons there is a limit to what can be achieved with this kind of curving of the sides.
CH 662 744 A5 describes a ski whose sides curve substantially inwards. As already mentioned, such skis will be difficult to control.